This invention concerns a diesel fuel and method for the cleaning out of deposits which adversely affect the performance of diesel engines. More particularly, this invention concerns the use of hydrocarbyl polyether polyamines as deposit control additives in diesel fuel in a concentration specifically designed to restore engine efficiency.
Until recently, in the United States, diesel engines were primarily limited to heavy uses such as trucks, farm equipment, and railroad engines. With the advent of the widespread acceptance of the passenger automobile utilizing a light-weight diesel engine, diesel fuels were required which did not give rise to severe noise and smoke problems such as those acceptable or tolerated in heavier engines.
Diesel fuels are susceptible to impurities which may arise from a variety of sources. They may occur in the fuel as produced or refined, or may through oxidation resulting from aging, produce soluble and insoluble materials of higher molecular weight and boiling point than the original fuel, which manifest themselves in the engine as colors or gums. Impurities may also be introduced in handling or from corrosion of storage vessels, either in the vehicle or in inventory. There may even be other additives specifically introduced by the manufacturer to solve or prevent some particular problem or improve the fuel itself, for example anti-oxidants, rust preventatives, and the like.
All of these impurities, however, may give rise to deposit formation in the fuel system of compression ignition engines, in particular, at the critical junctions of the fuel injectors. These deposits coat or adhere to injector parts and cause injector sticking, injector tip fuel metering passage fouling, nozzle hole plugging, leakage past critical surfaces, and delayed injection (and, hence, delayed start of combustion). These problems, in turn, result in significantly increased engine noise, smoke emissions, misfiring, low temperature or cold start problems, and idle roughness; and decreased power output and fuel economy.
It is believed that these engine problems are the result of long ignition delays, significantly contributed to by deposits, causing an excessively rapid pressure rise in the cylinder once combustion does occur. Recent evidence suggests that the long delay provides the time for certain chemical reactions to take place in the atomized fuel charge prior to ignition, resulting in products which burn exceedingly rapidly once combustion begins, thereby causing the undesirable rapid pressure rise, and the resultant problems. See "Gasoline and Other Motor Fuels-Diesel Fuel", Encyclopedia of Chemical Technology, Kirk-Orthmer, 3rd ed., Vol. 11, pp. 682-689.